#include <bits/stdc++.h>
using namespace std;

int main() {
	int n;
	cin >> n;
	int res = 0;
	while (n--) {
		int a, b;
		cin >> a >> b;
		if (b - a >= 2) {
			res++;
		}
	}
	cout << res << endl;
	return 0;
}